1. Field of the Invention
The present invention relates to bowling balls and more specifically relates to an insert for a finger hole in the bowling ball.
2. The Prior Art
When a mass-produced bowling ball is picked up by a player, it is necessary for the player to squeeze the gripping surface, which is smooth and has a relatively low coefficient of friction. The player may experience some apprehension that the ball will slip from his grip, particularly during his delivery, and repeated deliveries can result in fatigue of the muscles of the hand that grips the ball. If the gripping surface were of a softer and more resilient material with a higher coefficient of friction, it would not be necessary for the player to grip the ball so tightly.
This and other considerations have led bowlers to experiment with various ways of modifying the grip holes in the ball. Generally, however, when material is removed from the walls of the finger grips, the ball tends to become unbalanced. The American Bowling Congress requires for sanctioned play that the balance of the ball must be within certain specifications, which are relatively stringent. Therefore, when the finger grip holes of a bowling ball are enlarged to accept an insert, care must be taken that the balance of the ball is not disturbed unacceptably.
A number of inventors have worked on this problem, and their patents will be briefly discussed in the following paragraphs.
In U.S. Pat. No. 746,576 issued Dec. 8, 1903, Rice shows threaded inserts in the finger holes of a bowling ball, with weights located in a smaller coaxial hole that extends diametrically through and beyond the center of a bowling ball. The weights are not part of the inserts, but instead appear to be packaged within their own casings.
In U.S. Pat. No. 4,289,312, issued Sept. 15, 1981 to Heimbigner, there is described a resilient insert for a bowling ball. The bore of the insert is formed with an oval shape that matches the shape of the user's fingertip.
In U.S. Pat. No. 4,623,149, issued Nov. 18, 1986 to Herman, there is shown a resilient insert, the bore of which is provided with a plurality of grooves that extend circumferentially around the bore and that permit the user to maintain a better grip.
In U.S. Pat. No. 3,454,440, issued July 8, 1969 to Vezirakis, there is described a method for casting an insert for the thumb hole that conforms exactly to the shape of the user's thumb.
The following patents describe weights that are included in a bowling ball and that are adjustable: U.S. Pat. No. 863,126 issued Aug. 13, 1907 to Wilson; U.S. Pat. No. 3,591,177 issued July 6, 1971 to Skuse; and, U.S. Pat. No. 4,099,715, issued July 11, 1978 to Caplan.
The following patents describe weight blocks for balancing a bowling ball: U.S. Pat. No. 4,320,899 issued Mar. 23, 1982 to Salvino and U.S. Pat. No. 4,655,454, issued Apr. 7, 1987 to Amburgey.
None of the above inventors seems to have come to grips with the problem addressed by the present inventor. That problem is as follows. An existing thumb or finger hole must be enlarged to permit installation of an insert, to accommodate the wall thickness of the insert (typically a few millimeters). This removal of material from the wall of the hole disturbs the balance of the ball. The balance is not restored by the weight of the insert, because the material of the insert is typically less dense than the material of the ball. Unless remedial measures are undertaken, the ball will be out of balance after the insert has been installed.